Split breech block



June 24, 1958 J. G. LORD sm'r BREECH BLOCK Filed Aug. 18, 1955 6 Sheets-Sheet l R. 2 Wm H 0 m 5 i m J Y B lune 1953 J. G. LO RD 2,839,966

SPLIT BREE-CH BLOCK Filed Aug. 18. 1955 G'Sheets-Sheet 2 INVENTOR. 9 John G. L 0rd BY filflll m, I. www evm ql.

.ATTUR E25 Y June 24, 1958 J, G. 3RD 2,839,966

SPLIT BREEICH BLOCK ATT u'j lra June 24, 1958 J. G. LORD SPLIT BREECH BLOCK 6 Sheets-Sheet 4 Filed Aug. 18, 1955 June 24, 1958 J. G. LORD 2,839,966

SPLIT BREECH BLOCK Filed Aug. 18, 1955 6 Sheets-Sheet 5 5' 7/r 2:4 I I 5/ W W 5 I 1'9 22 I VENTQRR I John G. Lard:

June 24, 1958 J. G. LORD SPLIT BREECH BLOCK 6 Shee cs-Sheet 6 Filed Aug. 18, 1955 INVENTOR. John. B LDPEE ATTORNEYS.

SPLHT BREECH BLOCK John G. Lord, Swarthmore, Pa., assignor to the United States of America as represented by the Secretary of the Army Application August 18, 1955, Serial No. 529,369

7 Claims. (Cl. 822) This invention relates to breech loading mechanisms for rapid-fire guns.

The herein described invention'provides aabr'eech operating mechanism of particular value with gunsto be installed in places where available space is limited, such as in combat tanks, aircraft, etc.

An object of the invention is to provide a mechanism in which the breech block is split to form two halves of equal weight and moveable simultaneously and radially oppositely in the breech ring, whereby the total travel of the block parts is reduced with a corresponding reduetion in acceleration and deceleration forces.

Another object of the invention is to provide a mechanism in which the breech block parts move in atransverse plane parallel to a vertical plane through the gun trunnions, to eliminate any tendency of the gun to'tilt about its trunnions due to breech block acceleration in loading and extraction.

A still further object of the invention is to provide a gun having a two-part or split breech block wherein the forces necessary to move the parts between open and closed positions are equal and opposite and hence have minimum effect or reaction upon the gun mount.

Another object of the invention is to provide a mechanism having means to reduce shocks of opening and closing the breech, reduce the forces of acceleration, reduce maximum travel of breech block parts and prevent drifting of the block parts when in open or closed positions.

A further object of the invention is to provide means for time delay action of ammunition round extractors until the block parts have opened far enough to clear the exit for case of the spent round.

Other objects and advantages will be apparent from the following detailed description and the accompanying drawings, in which:

Figure 1 is a horizontal sectional view through the breech ring of a gun showing the breech block parts in closed position.

Figure 2 is a view similar to Figure 1 showing the reech block parts in open position.

Figure 3 is a vertical sectional view on the line 33 of Figure 1 with the gun barrel removed and looking toward the breechward end of the gun.

Figure 4 is an enlarged sectional view of a portion of the breech ring and the extractor assemblies during ramming movement of an ammunition round, t'akenon the line 4-4 of Figure 2.

Figure 5 is a similar View of one extractor assembly when the ammunition round is fully chambered in the gun barrel, taken on the same line as Figure 4.

Figure 6 is a view similar to Figure 5 showing a'position of one extractor assembly during extraction of the ammunition round, taken on the same line as Figure 4.

Figure 7 is an enlarged sectional view showing the positioning latch at the rearward end of extractor move= ment, taken on the line 7-7 of Figure 2.

Figure 8 is a detail sectional view taken on the line tates Patent "ice 8-8" of Figure 2 showing stop means'to limit rearward movement of the extractor assembly,

Figure 9 is a detail plan viewof the extractor latches in the position shown in Figure 6.

Figure 10 is an enlarged longitudinal section ofione formo'f buifer mechanism. a a i Figure 11 is an exploded perspective view of onel-of the breech block parts, the firing pin and the spring contacts on the vertical insert; I

Figure 12 is an exploded view to an enlarged scale of parts of the lower insert and one extractor assembly. Figure 13 is a detail sectional view taken on the line 1'? 13 of Figure 12, looking in the direction of the arrows. 1

Figure :14 is a similar view taken on the line 14-"-'14 of Figure 12'.

Figure '15 is a fragmentary horizontal sectional view 7 offone of the breech block parts and the firing pin, taken on the line 15-15 of Figure 3, looking in the direction of the arrows. V

Figure 16 is a perspective view of the breech block parts, the crank shafts and the links connected therebet-ween to' insure equal and opposite rotation of the crank shafts, looking from the rear end of the gun.

Figure 17' is an enlarged perspective view of the ex-' tractor base plate and breech blockconnecting links, and

Figure 18 is a detail sectional view on the line I818 of Figure '6" showing the pivot pins for mounting the-case latch" and position latch.

The t'erm"round' hereinafter used means a round of artillery ammunition. p

In the drawings, wherein for the purpose 'of' illustration is shown oneform of the invention, the numeral 1t) identifies a gun barrel. The barrel is provided with a'chamber 11 to receive a round 12, Figures 5 and 6.

A breech ring 13 is secured to the barrel byscrew threads ltttand' is formed with a transverse opening -15. A'split breech block comprising two parts E6 and 17' of equal size and weight are fitted to' slide in opposite irection :on inserts 18 and 19 fixed to the top and bottornsurfaces, respectively, of the transverse opening 15. The

inserts are of identical form and are positioned in the breech ring to slidab'ly guide upper and lowerextractor 'assemblies'20' and 21, respectively, to be-hereinafter more fullydescribed. As the inserts 1'8 and 19 are1alike-in structure a description of 19 will sufiice for both, see Figure 12. Insert 19 is generally in the form-of a flat plate having forward and rearward sections of different thicknesses which attheir juncture define a shoulder 22 with two faces 23 and 24 meeting at a large obtuse angle and inclined inwardly and forwardly to guide the block parts into close contact with the base of a chambered round. Secured against the rearward face of the transverseopeningIS in the breech block is a vertically disposedinsert 25, Figures 1, 2. and 11, havinga ce'nt'ral opening 26 axially aligned with a similar opening, an axial 1'oading aperature 27' in the breech ring. Q Bbth openings are in axial alignment withthegun chamber 11' fo provide entrance means for an incoming round and-exit means for it spent round. The forward'fac'e of'the'insert 25" is formed with angular faces 28' and2 9' parallel with the-angular faces 23 and '24 on'the inserts i8and 1 9 to cooperate therewith in guiding-the block p'a'rts. I

The upper insert 18, at its forward edge, is extended transversely-of the breech ring 13' and pierced to provide bearingsiti and '31. The lower insert 19 is similarly formed to provide bearings 32 and 33, see Figure 12'. A crankshaft 34-"is 'journalled for rotation in the bearings 30'and 32 at-tlie right side of the gun, lookingfforwardly, and asimilar crankshaft =35 is journalled for rotation in bearings 31 and 33, at the other side of the gun; See

of which is journaled a roller 42.

posite sides of the breech ring 13 in axial alignment with the respective pairs of bearings 30, 32 and 31, 33. The crankshafts 34 and 35 extend through bearing blocks 36 and 37 to a point below the breech ring. A crank arm 38 is secured to crankshaft 34 at its lower end and has an anti-friction roller 39 pinned for rotation in the free end thereof. Secured intermediate its ends to the lower endjof, crankshaft 35 is a double-armed lever 40, one

end 41 thereof having a stud shaft on the depending end The opposite end 43 of lever 40 is connected to the free end of crank arm 38 by a cross-link 44 to effect simultaneous and equal rotation of crankshafts 34 and 35.

Secured to the crankshaft 34 intermediate bearings 30 and 32, for rotation with the shaft is a multiple crank arm 45 pierced at its free ends to receive a pin 46. Vertically-spaced lugs 47 formed on the block part 17 are .pierced to receive a pin 48. Interposed between pins 46 and 48 is a multiple arm link 49 which with the crank arm 45 provides a toggle connection by which rotation of the shaft 34 is converted, in an obvious manner, into translation of block section 17. Similarly, a crank arm 50 identical with crankarm 45 is secured to the crank shaft 35 and is pierced at its free end to receive a pin 54, .corresponding to pin 46 at the other side of the breech.

Spaced lugs 51 on the block part 16 are pierced to receive a pin 53. Interposed between pins 53 and 54 is a multiple arm link 52 similar to the link 49 to connect the crank arm 50 and block part 16.

It will be apparent, by reference to Figures 1 and 2, that crank shafts 34 and 35 are constrained to equal and opposite rotations due to link connection 44 and that such rotations, by the toggle connections just described, will move the block parts simultaneously equally and oppositely in translation.

Cam structures 55 and 56 (see Figures 1, 2 and 3) are fixed to the gun cradle (not shown) on opposite sides of the breech ring and each lies in the path of a respective one of rollers 39 and 42 previously described as journaled on the lower crank arms 38 and 41. Each cam includes a rise 57 of a form to rotate the crankshafts 34 and 35, at an appropriate point in the recoil movement of the gun .and move the block parts from the closed position, Figure 1, to the open position, Figure 2.

The inserts 18 and 19 previously described, are formed with longitudinally extending guide grooves 58 (Figures 3 and 12) to slidably carry upper and lower extractor mechanisms 20 and 21, see also Figure 4. Each extractor mechanism comprises a base plate 59 having guide bars 60 slidable in the guide grooves 58, whereby the plates are guided for longitudinal translation only on and with respect to the inserts 18 and 19. The base plates are positioned in the transverse opening 13 in the breech ring and slidable in a plane parallel with the axis of the gun bore. The opposite ends 61 of the plate 59 are con- .nected to a respective breech block part 16 and 17 by ,links 62 and 63. Each link 62 is pivotally carried on the during inward and outward movement of the block parts.

Each cam is formed with a dwell 67 and a rise 68 (see Figure 2) to engage the rear face of the gun barrel when the cams are turned into the position shown upon Figure 2, whereby the plates 59 are forced rearwardly in an extraction movement. Transverse grooves or channels 69, Figure 12, are formed in the inserts 18 and 19 and have their inner ends 70 formed on the arc of a circle, as will be clear from inspection of Figures 1, 2 and 12. A roller .71 is rotatable on each pin 64 and is slidably guided in i and along a respective groove 69 to rotate its link 63 and cam 66 about the pivot element 65 to bring cam rise 68 into contact with the rear face of the gun barrel after a time delay eifected by the cam dwell 67 to provide initial extraction of a round from the chamber.

The extractors 20 and 21 and the cooperating details of the inserts 18 and 19 are similar so that a description of one will sufiice. An extractor lip 72 on the forward edge of base plate 59 projects inwardly into the path of the forward face of the base rim of round 12, see Figure 5. Two outwardly projecting transversely spaced lugs 73, Figures 3 and 8, are also formed on the forward edge of the base plate and abut similarly spaced stop plates 74 removably carried in stop holders 75, Figures 2, 3 and 8, held in grooves 76 by a spring-pressed pin 77. From Figure 8 it will be noted that each pin has a central flange 77a having a smooth fit Within a bore 19a in insert 19. The flange forms a stop limiting the upward movement of the pin under urge of a coil spring 19b and forming an abutment for the spring. An insert 19c fits a counterbore in the insert and is held in place by a snap ring 19d. The insert has a circular channel 19e in its upper face receiving and forming a lower abutment for the spring. The stop plates limit rearward movement of the extractor assembly during ejection of a round. Formed integral with top rearward surface of the base plate 59 is a bearing boss 78 which is pierced to receive a pivot pin 79. Mounted for limited rotation on the pivot pin is a stop latch 80 having a pawl 81 pivoted thereon and having its free end extending forwardly into engagement with and beneath the extractor lip 72 to limit inward rotational movement of the stop latch. A spring pressed plunger 82 'is carried in a bore in the stop latch 80 and bears against latches 85. The pivoted end of both pairs of latches 85 and 87 are connected for pivotal movement in opposite directions by segmental gear teeth 88 and 89 respectively,

.see Figure 7. The free ends of the latches 85 and 87 are normally urged apart under the bias of a helical spring 90 in a telescoped housing 90a which has its ends seated in depressions in the opposing surfaces of the latches.

The stop latch 80 of each extractor assembly travels in a central longitudinal depression or channel 91, in the insert 19, which extends from the front edge thereof rearwardly to a stop wall 92 on the shoulder 22 against which the stop latch abuts at its rearmost travel, Figure 4. Ramps 93 formed in the insert are positioned on each side of the central depression 91 and have formed therein notches 94 into which the free end of the position latch 87 enters to lock the extractor assembly in its rear position, Figure 7.

Two identical buffer mechanisms 95 are secured to the respective sides of the breech ring 13 to decelerate movement of the block parts near the ends of their inward and outward travel and to hold the parts against creep in either position. The right hand buffer mechanism (see Figure 10) is housed in av casing 96 having a cylindrical bore in which a piston 97 is fitted to reciprocate. Pins 98 are connected to the piston and extend transversely of the casing bore, through slots 99 in the casing. Slidabl'e with the pins 98 and restrained in guides 100 are closure plates 101 which act to prevent leakage of oil from within the casing. Links 102 (see Figures 1 and 10) connect the projecting ends of pins 98 with the pin 46 which connects the multiple crank arm 45 and multiple link 49. A one-way valve 103 formed in the piston 97 allows free fiow of oil'past the piston on recoil stroke of the gun and an orifice 104' retards theflow of oil on counter-recoil stroke thereof. A spring'105 within the casing exerts its bias agzinst the piston to close'the block parts after the rollers 39 and 41 have passed the cam rise 57 on counter-recoil movement of the gun. Bias of spring 105 can be regulated by a set-screw 126, threaded into the rear end of the buffer casing 96', and bearing on an abutment disk 125 in the buffer casing to back-up the spring 105. A similar buffer mechanism 95 is attached to the left side of the breech ringand is connected by its links 102 to the pin 54 which connects the multiple crank arm 50' and multiple links 52', Figures 1 and 2. The pivot pin 46' is forced off a center line running through the axes of pivot pin 48 and the crankshaft 34, by the links 102 of the buffer mechanism 95, in both open and closed block positions, to provide a toggle joint holding the block part 17 against creep. The links 52 and multiple crank arm 50 are similarly connected by the pivot pin 54 and buffer links to provide a toggle joint to hold the block part 16'.

Referring more particularly to Figures 11 and 15, a firing pin assembly is carried in one block part. In the present illustration the block part 16 is provided with a bore 106 angularly disposed to direct the pin assembly centrally of the gun chamber and with its forward end in registry with a primer (not shown) in the base of the round. The firing pin 107 is enclosed ina sheath 108 and insulated therefrom by a sleeve 109 of dielectric material. The sheath is enlarged diametricallyat its outer end 110 and has formed thereon a circumferential flange 111. The multiple arm link 52 includes an integral cylindrical spacer 112 on which a circumferential cam 113 is formed. Pivoted on a shaft 114 intermediate the lugs 51 of the block part 16 is a cam follower 115, forked at its end 116 to embrace the enlarged end 110 of sheath 108 and engage the circumferentiallflange 111. When the block parts are in closed position multiple arm link 52 and cam 113 are in the position shown in Figures 1 and 15. A bracket 117 is secured to the lugs 51 of block part 16 and supports a disk 118 insulated therefrom by a washer 119 of dielectric materi'al. A helical spring 120 at one end abuts the firing pin sheath and at its other end passes through an opening 121 in the bracket 117 and enters a recess or seat 122 in the disk 118; The firing pin and itssheath are normally projected inwardly by the bias of the spring 120. Formed on the disk 118 is a switch blade 123 which engages spring contact fingers 124 carried on the vertical insert 25 (Figures 11 and A source of voltage and suitable circuitry (not shown) is connected to the spring fingers 124 and directed to the firing pin to fire the round when the block parts move into fully closed position.

On recoil movement of the gun the multiple arm link 52 is rotated counterclockwise by'th'e crank arm 50, Figures 1 and 15 which is connected to the crankshaft 35, causing the cam follower 115 to ride on the rise of cam 113 and rotate on its shaft 114 and press its forked end 116 against the flange 111 on the firing pin sheath. The firing pin sheath is thus held retracted against the bias of helical spring 120 until the crankshaft 35 and crank arm 50 returns the link 52 and block part to closed position on counter-recoil movement of the gun.

During outward movement of the block part 16 the switch blade 123 leaves the spring contact fingers 124 and break connection with the source of voltage. On counter-recoil movement of the gun the movement of multiple arm link 52 is moved clockwise'rele'asing the cam follower from the cam rise, and the firing pinand sheath are projected inwardly into contact with the primer. The inward movement of block part 16 brings the switch blade into contact with the spring contact fingers and fires the round. I

The operation of the device is as follows:

Assuming the breech block parts 16' and 17 to be in open position, Figure 2, the buffer springs 105 urge the buffer pistons and links 102 forward to cooperate with the toggle joint formed by the crank arms 45 and 50 and the links 49'a'nd 52 to hold the block parts open. The base flange of an incoming round strikes the extractor lips 72 and causes the extractor assemblies to slide forward in the guide grooves 58' in the inserts 1'8 and 19. As the extractor assemblies move forward under the influence of inertia imparted thereto by the rammed round the breech block parts 16 and 17' are pulled in wardly by the links 62 and 63 against the bias of the buffer spring 105 thereby overcoming the resistance of the off-center position of the toggle joint to produce initial block closing. The buffer springs then move the block parts to closed position and the pins 46 and 54 connecting crank arms 45 and 50 and the links 49 and 52 pass dead' center to form a toggle joint holding the breech block parts closed against rebound or creep. The cross link 44 connects the crank shafts 34' and 35 for equal inward and outward movement by means of the crank arms 38 and 43.

In block open position the extractor assemblies are positioned as shown in Figure 4, wherein the outer ends of the stop latches contact the stop walls 92 of the shoulders 22 and 23 on the inserts 18 and 19 to prevent rearward movement of theassemblies. Forward movemerit of the extractor assemblies is prevented by the position latch 87 whose forward end is held in a notch 94 formed in the ramp 93. The position latch 87 is connected to the case latch by the meshing gear teeth 83 and 89 for simultaneous movement. The spring '90 biases the latches apart and forces the free end of the position latch 87 into the notch 94. Before the base flange of the incoming round reaches the extractor lip 72 it first cams down the case latch 35 and through its gear connection therewith the position latch 87 is moved out of the notch 94 to ride on the top of ramp, 93'. Further forward movement of the base flange of the round cams down the stop latch 80 and forces its outer end against the stop wall 92 to give the assembly an initial forward movement. of the round brings its base flange into contact with the extractor lip 72, thereafter the round and extractor assembly move together to full chambered positionrof the round. Before the end of the forward travel of the extractor assembly the free end of the position latch 87 rides down the inclined end of ramp 93 and the bias of spring forces latches 85 and 87 apart causing the free end of latch 85 to rise behind the base flange of the round against rebound, Figure 5. When the round is fired and the gun recoils rollers 39 and 42 ride up on the rises 57 of the cams 55 and 56, see Fig. 1, and rotate the crank shafts 34 and 35 through crank arms 38 and 41. Crank arm 45 and 50 swing outwardly pulling the block parts 16 and 17 apart by means of the connecting multiple links 49 and 52. When the block parts have moved far enough apart to permit ejection of the round, the links 62 and 63 which connect the block parts and the extractor base plate 59 are moved from the position shown in Figure 1 toward the position shown in Figure 2. During this movement the links 63 are, rotated about their pivotcom nections 65, guided by the rollers 71 in grooves 70 in the inserts 18 and 19. The cams 66 abut the rear face of the gun barrel and exert no force thereagainst while the cam dwell 66 remains in contact with the barrel, but as the links 63 are rotated further cam rises 68 come into contact with the rear face of the barrel and breaks the round loose from its chamber. Blow-back pressure in the gun bore accelerates the rearward movement of the spent case and during this movement the extractor assembly moves rearwardly with the case until the free end of the position latch 87 rides on ramp 93 retracting the case latch 85 from behind the base flange and freeing the spent case for ejection by blow-back. By this time the extractor assembly has reached a rearmost position due to' inerti a imparted thereto by the'spent case, at which Further forward movement time the outer end of the stop latch 80 abuts the stop wall 92 and the free end of position latch is again seated in the notch 94. By this time the block parts have reached the full open position. During the opening movement of the block parts the bufier piston can move rearward quickly due to the one way valve 103 therein but returns slowly due to the restricted passage of oil through the orifice 104. On counter-recoil movement of the gun the buffer spring 105 returns the block parts to closed position.

The upper extractor 20 sliding in the upper insert 18 is identical with the lower extractor 21 in structure and operation and the two extractors serve to firmly grip the base flange of a round for ramming and extraction. The operation of the firing pin has been fully described hereinbefore and further discussion is unnecessary.

While I have disclosed a form of the invention presently preferred by me, various changes and modifications will occur to those skilled in the art after a study of the present disclosure. Hence the disclosure is to be taken in an illustrative rather than a limiting sense; and it is my desire and intention to reserve all modifications falling within the scope of the subjoined claims.

Having now fully disclosed the invention, what I claim and desire to secure by Letters Patent is:

1. In a rapid-fire recoil operated gun, the combination comprising a breech ring, a two part breech block slidable horizontally in said breech ring in a vertical plane parallel to a similar plane passing through the horizontal axis of rotation of the gun, a link and lever system connecting said block parts for simultaneous movement to open and closed positions, a fixed cam having a rise, anti-friction means in said link and lever system riding said cam rise during recoil movement of the gun to move said block parts to open position and riding ofi said rise at the end of counter-recoil movement thereof, means connected to said block parts to initiate closing movement of said block parts by and in response to movement of a round of ammunition into the breech of said gun, and means to complete closing said block parts.

2. In a rapid-fire recoil operated gun, the combination comprising a breech ring, a two-part breech block slidable in said breech ring, means connecting said block parts for simultaneous movement in equal and opposite directions to open and closed positions, a fixed cam, said block connecting means including mechanism engaging said cam to move said breech block parts to open position on recoil movement of the gun, an extractor mechanism slidable in said breech ring, an extractor lip in said extractor mechanism, second means connecting said block parts and extractor mechanism to initiate inward movement of said block parts by and in response to ramming movement of a round of ammunition against said extractor lip, and buffer means connected to said first connecting means to complete inward movement of said block parts.

3. In a rapid-fire recoil operated gun, the combination comprising a breech ring, a two-part breech block slidable horizontally in said breech ring, a crankshaft journalled for rotation on each side of said breech ring, a first crank arm on said crankshaft, a link connecting each crank arm and respective block part, a second crank am secured to each said crankshaft for rotation therewith and having a roller journalled for rotation in the outer end thereof, a cross-link connecting said second crank arms to insure simultaneous opposite movement of said crankshafts and block parts, a fixed cam in the path of said roller to effect rotation of said crank arm and shaft on recoil movement of said gun, an extractor assembly slidable in said breech ring, multiple link means connecting said block parts and extractor assembly, an extractor lip in said extractor assembly in the path of the base flange of an incoming ammunition round whereby inertia of said round is transferred to said extractor assembly and said multiple link means to initiate closing of said block parts when the ammunition round is fully chambered in the gun, and a bufier mechanism connected to said first crank arm and link to complete closing of said block parts.

4. In a rapid-fire recoil operated gun, the combination comprising a breech ring, a two-part breech block slidable in said breech ring, a crankshaft journalled for rotation on each side of said breech ring, a first crank arm on each said crankshaft, a link pivotally connected to said crank arm and respective block part, a second crank arm on each said crankshaft for rotation therewith and having its free end extending beyond the breech ring in breech closed position, a fixed cam in the path of the extended end of said second crank to effect rotation of said crankshaft on recoil movement of said gun, a cross-link connecting said second crank arms to insure simultaneous opposite movement of saidshafts and block parts, an extractor assembly slidable in said breech ring, multiple link means connecting said block parts and extractor assembly an extractor lip in said extractor assembly to receive the thrust of an incoming ammunition round, and latch means movable with said extractor lip to secure the round against rebound when fully chambered at the end of counter-recoil movement and releasing the round for ejection by the said extractor lip on recoil movement of said gun.

5. In a rapid-fire recoil operated gun, the combination comprising a breech ring, a two-part breech block slidable horizontally in said breech ring in equal and opposite directions to open and closed positions, a crankshaft journalled for rotation on each side of said breech ring, first link means connecting each crankshaft and respective block part and including a toggle joint, a crank arm secured to each said crankshaft for rotation therewith and having a roller journalled for rotation in the outer end thereof, a cross-link connecting said crank arms to insure simultaneous opposite movement of said shafts and block parts, a fixed cam in the path of said roller to eflfect rotation of said crank shaft on recoil movement of said gun to open said block parts, a buffer mechanism including a rod connected to the toggle joint of said first link means to decelerate outward movement of said block parts and retain them in open position, an extractor assembly slidable in said breech ring, second link means connecting said block parts and extractor assembly including a link pivotally secured at one end to said extractor mechanism and having a cam element on said pivoted end to be rotated into contact with the breech end of said gun initiating extraction of a round of ammunition after a predetermined dwell in said cam element delaying extraction of a fired round until said block parts have opened a sulficient distance for round ejection and thereafter completing ejection of the round, and a buifer mechanism connected to, said toggle joint to decelerate further outward movement of said block parts to full open position and locking said block parts against creep.

6. In a rapid-fire recoil operated gun, the combination comprising a breech ring, a two-part breech block slidable in said breech ring each block part having a pair of attaching lugs on their outer faces, a crankshaft journalled for rotation on each side of said breech ring, a multiple crank arm on each said crankshaft, a multiple arm link pivotally connected to said crank armat one end and having its opposite ends connected by an integral cylindrical spacer, a pivot pin extending through said spacer and. block part attaching lugs, a cam secured to one said cylindrical spacer, a spring pressed firing pin assembly slidable in the adjacent block part, a cam follower pivoted between said attaching lugs and having one end operable in response to rotation of said spacer and cam and its opposite end operable to retract said firing pin assembly when said block parts are in open position, a switch blade carried by said firing pin assembly, a spring contact carried in said breech ring, a source of voltage connected to said spring contact to fire a round in said gun when said block parts are in closed position and said switch blade engages said spring contact, a single crank arm on lower end of each crankshaft, a cross link connecting each single crank arm to effect simultaneous opposite movement of said crank shafts and block parts,

and cam means engageable with said single crank arms to open and close the breech block parts in response to recoil and counterrecoil movements of the gun.

7. In a rapid fire recoil operatedgun the combination comprising a two-part breech block mounted adjacent the breech of said gun slidaole from an open to a closed position, connecting means connecting said block parts for simultaneous movement of said parts from said open to said closed positions, a firing pin mounted in one of said block parts for movement from a non firing to a firing position when said one of said block parts moves from said open to said closed position respectively, breech block closing means connected to said block parts to initiate movement of said =block parts 'towards said closed position by contact thereof with a round of ammunition when said round is moved into the breech of said gun.

References Cited in the file of this patent UNITED STATES PATENTS 2590,9231 t'Lippert Apr. 1, 1952 

